Goniometers are apparatus which are used by physiotherapists and the like to measure anatomical angles of a body. For example, they are often used to measure the range of angular motion of joints.
The following patent documents disclose examples of known goniometers as well as other apparatus for measuring angles: U.S. Pat. No. 4,771,548 (Donnery), United States Patent Application Publication No. 2006/0137201 A1 (Dixon, et al.), U.S. Pat. No. 6,469,666 (Tonn), U.S. Pat. No. 7,337,751 (Lopez, et al.), U.S. Pat. No. 4,442,606 (Graham, et al.), U.S. Pat. No. 7,204,030 (Kattar), U.S. Pat. No. 7,293,363 (Emmett L. Parker), United States Patent Application Publication No. 2007/0266579 A1 (Briscoe, at al.), U.S. Pat. No. 5,163,228 (Edwards, et al.), U.S. Pat. No. 4,665,928 (Linial, et al.), U.S. Pat. No. 3,879,136 (Takeda), U.S. Pat. No. 4,665,928 (Linial, et al.), United States Patent Application Publication No. 2003/0226268 A1 (Gibson), U.S. Pat. No. 7,359,750 (Song, et al.), U.S. Pat. No. 5,253,655 (Stone, et al.), and International Patent Application No. PCT/DE1993/000891.
Many existing goniometers include a pair of aligning arms which are able to pivot relative to each other. In use, each arm is aligned with anatomical landmarks which are adjacent to the body part whose angle is being measured. For example, if a goniometer with arms is used to measure the angle between the upper part of a person's leg and the lower part of their leg, one of the arms of the goniometer will be aligned with landmarks on the upper part of the leg while the other arm is aligned with landmarks on the lower part of the leg. Once the arms have been properly aligned with the upper and lower leg parts, the angle between the arms corresponds to the angle between the leg parts and can be read off an analogue scale of the goniometer.
Goniometers of the above-described type suffer from the disadvantage that the arms are often not tong enough to accurately align them with some anatomical landmarks. When this situation arises, the person using the goniometer will usually use an eye-balling approach to align the arms with the landmarks as best they can. The accuracy of the measurement which is obtained will be reduced if the arms are not property aligned with the landmarks.
Although this problem can be overcome by extending the length of the arms (e.g. by making the arms extendable) so that they are able to reach all of the landmarks that they need to be aligned with when making a measurement, doing so would make the arms somewhat of an obstruction to a user and also make them more vulnerable to being broken or bent.
Measurement inaccuracy can also be introduced by the analogue scale of the goniometer from which the angle measurement is read. This is because the user needs to interpret the reading from the scale. Although some devices include a digital display which can address this problem, the displays tend to be small and difficult to read.
For various reasons, including those given above, many existing goniometers have poor inter therapist reliability because the variability of readings from one user to another tends to be significant. For example, there can be a 5-10 degree variance between different users. Similarly, many existing goniometers have poor intra therapist reliability because the variability of readings from the same user tends to be significant. As a consequence, measurements obtained from such goniometers are generally not taken seriously.
The inaccuracy and variance of readings obtained from existing goniometers can have significant negative consequences. For example, if a post-operative patient who has had a joint operated on must gain a certain amount of range of motion in that joint before they are able to be discharged from hospital, and if a therapist uses a goniometer to measure the range of motion of the joint to determine whether or not the patient has gained the required amount of motion, the date on which the patient is discharged will be unnecessarily delayed if the patient does have the required range of motion but, due to an inaccurate measurement obtained from the goniometer, the measured range indicates that they do not have the required range. An unnecessary delay in the patient being discharged means that the patient will needlessly be occupying a hospital bed which should be made available to someone else.
Another problem with many existing goniometers is that a user often needs to operate them with both of their hands. This means that while they are performing a measurement with such a device they do not have a hand available to assist the person on whom they are performing the measurement, or to write down the measurement which is obtained from the device.
Furthermore, many existing goniometers (particularly those which have aligning arms) are quite bulky. This bulkiness can contribute to the need for users to operate them with both hands.
Existing goniometers which have short aligning arms and/or analogue scales can also be time-consuming to use, particularly if an accurate measurement is required. This is because it can take time to properly align the arms with landmarks that the arms cannot reach, and because it can take time to properly read the scale.
In addition, at present, different sized goniometers are required to obtain measurements of different sized joints. A large goniometer is required in order to take measurements for the hip and other large joints. A small goniometer is required in order to take measurements of medium size joints and also to take measurements on the pediatric population. A finger joint goniometer is required in order to measure the angle of finger joints.
It is against this background that the present invention has been developed.